Such a method, is known from "SOLID STATE TECHNOLOGY, Volume 30, No. 10, pages 49-50. According to that method deposition is realized in a process chamber in which several wafers are positioned on the same horizontal plane adjacent to each other. For loading and unloading, it is necessary to rotate the wafers on a horizontal table to position them before a pick-up device. Except for the considerable floor requirement of such a device, the transport path of the several wafers is relatively long. This impairs the effectiveness and cleanliness of the processes in the process chambers.
In the solid state technology there is a continuous tendency to increase wafer size. Because of the increased wafer size at a given space for a horizontal table the number of wafers which can be processed simultaneously decreases, increasing processing costs. Increasing table size has structural limits. Furthermore problems have been encountered during evacuating the above chamber, because of the relatively large sealing surfaces.
The invention aims to provide a method in which deposition can be realized in an effective way both with regard to time and costs, and wherein cleanliness of several processes in the system can be guaranteed by shortening the transport path.
According to the invention this is realized with the characterizing features recited in the claims.
In U.S. Pat. No. 4,717,461 a method is described for depositing a layer on a substrate by sputtering. After being introduced into a loading/unloading station, the substrate is transferred to a treatment chamber. After a layer has been deposited, it is then subjected to an etching procedure in order to achieve the required configuration. Characteristic is the fact that the treatment stations can hold and treat only one substrate at the same time.
Sputtering has a number of advantages and disadvantages. Characteristic of sputtering is the ballistic nature of the process. As a result of this, it is ultimately impossible to provide deep narrow holes and grooves, which are typical of the structure in, for example, megabit patterns, uniformly with a layer or to remove a layer. For this reason, chemical vapour deposition of materials at elevated temperature is also used in the prior art. Such a method is described, for example, in GB-A 2,190,345. In that case, the substrates are transferred directly into a processing furnace. In doing so, however, problems arise in relation to contaminants present on the surface. Metal ion contaminants left behind may be regarded in the first place as contaminants, but the substrate oxide, which is always produced when the substrate is exposed to the air, must also be perceived as such. A final contaminant is represented by molecules adsorbed on the substrate (primarily hydrocarbons).
In the case of sputtering, any contaminants present are removed from the surface by a bombardment with high-energy (50 eV and higher) atoms before the sputtering treatment is started, the so-called sputter etch. A disadvantage of this etching process is the production of damage to, and defects in, the crystal lattice of the substrate as a result of the incidence of the bombarding atoms. The incident atoms penetrate the substrate and, together with a certain fraction of the contaminants, are trapped in the top layer of the substrate. The more the technology advances and increasingly higher requirements have to be imposed on the integrity of the increasingly thinner layers, the more the above-mentioned sputter etch is increasingly inadequate and a search has to be made for methods in which the substrate oxide and the atoms adsorbed on the substrate are removed without undesirable atoms being incorporated in the top layer of the substrate and without defects in the crystal lattice of the substrate being the result of the cleaning process. In addition, it is necessary to ensure that the cleaned surface is not exposed to the air again. In the case of chemical vapour deposition, there is the advantage that structures can be uniformly provided with a layer, but there is the disadvantage that such a cleaning does not take place in the same apparatus. This is one of the big disadvantages of chemical vapour deposition in which use has hitherto been made of separate apparatuses for the removal of contaminants and the application of layers.